The present invention relates generally to the field of hydraulic pumps, and in particular but not by way of limitation, to a hydraulic actuator used in a marine environment in conjunction with an outboard motor.
The need for portable lifting power is widespread. Batteries provide a good source for power but the driven devices can be complicated, cumbersome and inadequate. To date, the most popular systems are driven by direct current (DC) electric motors. These motors generally drive screw type devices or hydraulic type devices. Screw type devices have proven adequate for some light duty applications but fall short when long-term rugged service is required. Hydraulic devices are inherently more suited to harsh service but tend to be more complicated and expensive.
Most hydraulic lifting systems consist of several separate components such as a motor, hydraulic pump, hydraulic fluid reservoir, hydraulic lines, assorted fittings, electric control solenoids and a hydraulic cylinder. These systems are functional but impractical for many portable applications, since each component must be mounted independently to operate as a unit. Space and weight restrictions are problems since each component must have a housing or enclosure.
Harsh environments also pose problems for these systems. Most hydraulic systems require use of breather tubes or vents that allow contaminants such as water, dirt and other foreign objects, to enter the system and such contamination often leads to component failure. The components are usually made from ferrous materials, making the components susceptible to corrosion.
Thus, prior art hydraulic systems have been found to be undesirable for marine applications.
The present invention provides a hydraulic actuator suitable for use in marine and other harsh environments. In the presently preferred embodiment, the hydraulic actuator includes a motor that is configured to operate in a first or second direction. A pump assembly is coupled to the motor and is configured to pressurize and displace hydraulic fluid. The hydraulic actuator also includes a cylinder bore that has an upper chamber and a lower chamber which are separated by a movable piston member. A first plurality of pressure actuated valves are used to regulate the flow of high pressure hydraulic fluid to the upper chamber and low pressure fluid from the lower chamber. The first plurality of pressure actuated valves are actuated in response to pressure generated by the pump assembly when the motor is operating in the first direction. A second plurality of pressure actuated valves are used to regulate the flow of high pressure hydraulic fluid to the lower chamber and low pressure fluid from the upper chamber. The second plurality of pressure actuated valves are actuated in response to pressure generated by the pump assembly when the motor is operating in the second direction.